1. Technical Field of the Invention
The present invention relates to tools for cleaning an auger, in particular but not exclusively a continuous flight auger, as it is being withdrawn or after it has been withdrawn from the ground.
2. Prior Art
Augers are commonly used in civil engineering applications such as piling, a particular example of this being Continuous Flight Auger (CFA) piling. A continuous flight auger comprises a generally cylindrical elongate body provided with a generally helical blade. Each 360.degree. turn of the auger defines a flight of the blade, i.e. a flight is the space between adjacent, longitudinally-spaced sections of the blade. In use, the auger is rotated into the ground to a predetermined depth at which the downward advance of the auger is halted. The auger may then be withdrawn without further rotation, thereby shearing a "plug" of soil directly from the ground so as to form a bore hole, or the auger may be rotated before withdrawal so as to shear the soil on the flights from the soil which will eventually form the wall of the resultant bore hole. During withdrawal, concrete or grout may be pumped through the auger or down a feed pipe under positive pressure so as to form a cast-in-situ pile.
Upon withdrawal, the flights of the auger are generally loaded with soil, and there is a danger that some of this soil will become locked between adjacent flights instead of falling out cleanly as the auger emerges above ground level. As the auger continues to be withdrawn, the flights with the locked-in soil will be raised to levels some distance (typically up to 20 m) above the ground, and there is a significant danger that the locked-in soil may loosen and fall onto operating personnel on the ground, possibly causing serious injury. This is becoming more of a problem with modern CFA piling techniques, since these often require a tight entry into the ground which results in soil being packed onto the flights in a particularly dense and compact manner.
Traditionally, augers have been cleaned by hand, for example by using a scraping implement and sometimes water jets. This, however, is labour intensive and can be dangerous.
It is known from GB 2 235 480 A (amongst others) to scrape soil off the flights of a rotating auger by deploying a toothed wheel next to the auger in the manner of a worm drive. As the auger rotates, so does the wheel, the teeth of the wheel engaging between the flights and thereby scraping off locked-in soil. This technique is not particularly effective, since only soil locked in a single flight is attacked at any one time. Furthermore, if the auger is being withdrawn rather than merely being rotated out of the ground, then the toothed wheel will tend to miss sections of the auger flights.